No abstract

We represented herein a synthetic endeavor to the epoxy-lactone moiety that is commonly present in the C/D ring of highly oxygenated triterpene. Two strategies were applied to the synthesis based on the ursolic acid, namely, the Br+-promoted cyclization isomerization for late-stage epoxidation and the one-step SeO2-promoted oxidative cyclization. Finally, the desired epoxy-lactone moiety could be readily prepared on gram-scale in one step using our modified SeO2/TBHP/AcOH oxidative system.